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Math Help - Bacteria growth question with formula

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    Bacteria growth question with formula

    Could someone please help me with this problem! Thanks! #29
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by aikenfan View Post
    Could someone please help me with this problem! Thanks! #29
    First, we need to find k

    (Note that 100 is the initial size)

    We are told when N = 300, t = 5, so plug those in:

    \Rightarrow 300 = 100e^{5k}

    Now solve for k.

    Once you have k, put it in the original formula. then plug in N = 200 and solve for t, that will give you the required time


    Any questions?
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    i get .2197 for k
    do i have to double the 300 as well or just the 100?
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by aikenfan View Post
    i get .2197 for k
    correct!

    do i have to double the 300 as well or just the 100?
    now that we know k, we have:

    N = 100 e^{0.2197t}

    now plug in N = 200 (since that is double 100 -- the initial population size) and solve for t

    you were just given the 300 to find k, now that you have, forget about it. i believe the question is asking how long it takes to double from the initial population (i may be wrong)

    all i know, you only have to use one or the other, not both. if you want to find how long it takes to double from 300, then plug in N = 600 and solve for t, then subtract 5 from the answer
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    why do i subtract 5?
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by aikenfan View Post
    why do i subtract 5?
    i was thinking they would want the time required to double, since it was 300. it was 300 at 5 seconds, so to find the additional seconds, need to subtract 5 from the total time it took to get to 600
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